The production of cam shafts or control shafts in general is usually made by joining individual components, for example, bearings and cams, on the camshaft, whereupon the camshaft is then ground, in particular in the area of the cams, and thereby finish-treated. Specifically during this finish treatment by grinding, grinding dust is produced which can penetrate into the bearing or in particular into the bearing surfaces, settle there and during subsequent operation of an internal combustion engine fitted with the camshaft, can result in increased wear and in the most unfavourable case, even in damage to the bearings. For this reason, it is known to protect the bearings, for example roller or needle bearings, from contamination during grinding of the cams by manually applied cages. However, these cages must be laboriously screwed on manually and unscrewed again after the actual grinding process, which is not only time-consuming but also cost-intensive.